klarkxy/hustoj
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
Files
master
hustoj/web/cppreference-zh/chmhelp/cpp-string-basic_string_view-starts_with.html
klarkxy 196e706fe4 上传cppreference
2025-08-01 12:57:54 +08:00

174 lines
12 KiB
HTML
Raw Permalink Blame History

<!DOCTYPE html>
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>std::basic_string_view&lt;CharT,Traits&gt;::starts_with</title>
<link rel="stylesheet" href="ext.css" />
<link rel="stylesheet" href="site_modules.css" />
</head>
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_string_basic_string_view_starts_with skin-cppreference2 action-view cpp-navbar">
<div id="cpp-content-base">
<div id="content"><a id="top"></a>
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::basic_string_view&lt;CharT,Traits&gt;::</span>starts_with</h1>
<div id="bodyContent">
<div id="contentSub"><span class="subpages">&lt; <a href="cpp.html">cpp</a>&lrm; | <a href="cpp-string.html">string</a>&lrm; | <a href="cpp-string-basic_string_view.html">basic string view</a></span></div>
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
<table class="t-dcl-begin">
<tbody>
<tr class="t-dcl t-since-cxx20">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">bool</span> starts_with<span class="br0">(</span><a href="cpp-string-basic_string_view.html"><span class="kw1246">std::<span class="me2">basic_string_view</span></span></a> sv<span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td>(1)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">bool</span> starts_with<span class="br0">(</span>CharT c<span class="br0">)</span> <span class="kw4">const</span> <span class="kw1">noexcept</span><span class="sy4">;</span></span></div>
</td>
<td>(2)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
<tr class="t-dcl t-since-cxx20">
<td>
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">bool</span> starts_with<span class="br0">(</span><span class="kw4">const</span> CharT<span class="sy2">*</span> s<span class="br0">)</span> <span class="kw4">const</span><span class="sy4">;</span></span></div>
</td>
<td>(3)</td>
<td><span class="t-mark-rev t-since-cxx20">(C++20 &#36215;)</span></td>
</tr>
<tr class="t-dcl-sep">
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>
<p>&#26816;&#26597; string_view &#26159;&#21542;&#22987;&#20110;&#32473;&#23450;&#21069;&#32512;&#65292;&#20854;&#20013;</p>
<div class="t-li1"><span class="t-li">1)</span> &#21069;&#32512;&#20026; string_view &#12290;&#31561;&#25928;&#22320;&#36820;&#22238; <span class="t-c"><span class="mw-geshi cpp source-cpp">substr<span class="br0">(</span><span class="nu0">0</span>, sv.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="br0">)</span> <span class="sy1">==</span> sv</span></span></div>
<div class="t-li1"><span class="t-li">2)</span> &#21069;&#32512;&#20026;&#21333;&#20010;&#23383;&#31526;&#12290;&#31561;&#25928;&#22320;&#36820;&#22238; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="sy3">!</span>empty<span class="br0">(</span><span class="br0">)</span> <span class="sy3">&amp;&amp;</span> Traits<span class="sy4">::</span><span class="me2">eq</span><span class="br0">(</span>front<span class="br0">(</span><span class="br0">)</span>, c<span class="br0">)</span></span></span></div>
<div class="t-li1"><span class="t-li">3)</span> &#21069;&#32512;&#20026;&#31354;&#32456;&#27490;&#23383;&#31526;&#20018;&#12290;&#31561;&#25928;&#22320;&#36820;&#22238; <span class="t-c"><span class="mw-geshi cpp source-cpp">starts_with<span class="br0">(</span>basic_string_view<span class="br0">(</span>s<span class="br0">)</span><span class="br0">)</span></span></span></div>
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">&#21442;&#25968;</span></h3>
<table class="t-par-begin">
<tr class="t-par">
<td>sv</td>
<td>-</td>
<td>&#21487;&#33021;&#20026;&#26469;&#33258; <code>std::basic_string</code> &#36716;&#25442;&#32467;&#26524;&#30340;&#23383;&#31526;&#20018;&#35270;&#22270;</td>
</tr>
<tr class="t-par">
<td>c</td>
<td>-</td>
<td>&#21333;&#20010;&#23383;&#31526;</td>
</tr>
<tr class="t-par">
<td>s</td>
<td>-</td>
<td>&#31354;&#32456;&#27490;&#23383;&#31526;&#20018;</td>
</tr>
</table>
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">&#36820;&#22238;&#20540;</span></h3>
<p>&#33509; string_view &#22987;&#20110;&#32473;&#23450;&#21069;&#32512;&#21017;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">true</span></span></span> &#65292;&#21542;&#21017;&#20026; <span class="t-c"><span class="mw-geshi cpp source-cpp"><span class="kw2">false</span></span></span> &#12290;</p>
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">&#31034;&#20363;</span></h3>
<div class="t-example">
<div class="t-example-live-link"></div>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="cpp source-cpp">
<pre class="de1"><span class="co2">#include &lt;iostream&gt;</span>
<span class="co2">#include &lt;string_view&gt;</span>
<span class="kw4">auto</span> main<span class="br0">(</span><span class="br0">)</span> <span class="sy2">-</span><span class="sy1">&gt;</span> <span class="kw4">int</span>
<span class="br0">{</span>
<span class="kw1">using</span> <span class="kw1">namespace</span> std<span class="sy4">::</span><span class="me2">literals</span><span class="sy4">;</span>
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a>
<span class="sy1">&lt;&lt;</span> <a href="cpp-io-manip-boolalpha.html"><span class="kw1764">std::<span class="me2">boolalpha</span></span></a>
<span class="co1">// bool starts_with(basic_string_view x) const noexcept;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;https://cppreference.com&quot;</span>sv.<span class="me1">starts_with</span><span class="br0">(</span><span class="st0">&quot;http&quot;</span>sv<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// true</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;https://cppreference.com&quot;</span>sv.<span class="me1">starts_with</span><span class="br0">(</span><span class="st0">&quot;ftp&quot;</span>sv<span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// false</span>
<span class="co1">// bool starts_with(CharT x) const noexcept;</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;C++20&quot;</span>sv.<span class="me1">starts_with</span><span class="br0">(</span><span class="st0">&#39;C&#39;</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// true</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&quot;C++20&quot;</span>sv.<span class="me1">starts_with</span><span class="br0">(</span><span class="st0">&#39;J&#39;</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// false</span>
<span class="co1">// bool starts_with(const CharT* x) const;</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a><span class="br0">(</span><span class="st0">&quot;string_view&quot;</span><span class="br0">)</span>.<span class="me1">starts_with</span><span class="br0">(</span><span class="st0">&quot;string&quot;</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// true</span>
<span class="sy1">&lt;&lt;</span> <a href="cpp-string-basic_string_view.html"><span class="kw1248">std::<span class="me2">string_view</span></span></a><span class="br0">(</span><span class="st0">&quot;string_view&quot;</span><span class="br0">)</span>.<span class="me1">starts_with</span><span class="br0">(</span><span class="st0">&quot;String&quot;</span><span class="br0">)</span> <span class="sy1">&lt;&lt;</span> <span class="st0">&#39; &#39;</span> <span class="co1">// false</span>
<span class="sy1">&lt;&lt;</span> <span class="st0">&#39;<span class="es1">\n</span>&#39;</span><span class="sy4">;</span>
<span class="br0">}</span></pre></div>
</div>
<p>&#36755;&#20986;&#65306;</p>
<div dir="ltr" class="mw-geshi" style="text-align: left;">
<div class="text source-text">
<pre class="de1">true false true false true false</pre></div>
</div>
</div>
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">&#21442;&#38405;</span></h3>
<table class="t-dsc-begin">
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-string-basic_string_view-ends_with.html"><span class="t-lines"><span>ends_with</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597; string_view &#26159;&#21542;&#32456;&#20110;&#32473;&#23450;&#21518;&#32512;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-string-basic_string-starts_with.html"><span class="t-lines"><span>starts_with</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597; string &#26159;&#21542;&#22987;&#20110;&#32473;&#23450;&#21069;&#32512;<br />
<span class="t-mark">(<code>std::basic_string&lt;CharT,Traits,Allocator&gt;</code> &#30340;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-string-basic_string-ends_with.html"><span class="t-lines"><span>ends_with</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx20">(C++20)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597; string &#26159;&#21542;&#32456;&#20110;&#32473;&#23450;&#21518;&#32512;<br />
<span class="t-mark">(<code>std::basic_string&lt;CharT,Traits,Allocator&gt;</code> &#30340;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-string-basic_string-contains.html"><span class="t-lines"><span>contains</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597;&#23383;&#31526;&#20018;&#26159;&#21542;&#21547;&#26377;&#32473;&#23450;&#30340;&#23376;&#20018;&#25110;&#23383;&#31526;<br />
<span class="t-mark">(<code>std::basic_string&lt;CharT,Traits,Allocator&gt;</code> &#30340;&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-string-basic_string_view-contains.html"><span class="t-lines"><span>contains</span></span></a></div>
<div><span class="t-lines"><span><span class="t-mark-rev t-since-cxx23">(C++23)</span></span></span></div>
</div>
</td>
<td>&#26816;&#26597;&#23383;&#31526;&#20018;&#35270;&#22270;&#26159;&#21542;&#21547;&#26377;&#32473;&#23450;&#30340;&#23376;&#20018;&#25110;&#23383;&#31526;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
<tr class="t-dsc">
<td>
<div class="t-dsc-member-div">
<div><a href="cpp-string-basic_string_view-compare.html"><span class="t-lines"><span>compare</span></span></a></div>
</div>
</td>
<td>&#27604;&#36739;&#20108;&#20010;&#35270;&#22270;<br />
<span class="t-mark">(&#20844;&#24320;&#25104;&#21592;&#20989;&#25968;)</span></td>
</tr>
</table>
</div>
<div class="visualClear"></div>
</div>
</div>
</div>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink